1. Field of the Invention
The present invention relates to a solid-state imaging device, and more particularly to a solid-state imaging device that suppresses crosstalk of light.
2. Description of the Related Art
In a solid-state imaging device, e.g., a device such as a CMOS image sensor, a pixel size is reduced for the purpose of realizing a miniaturization, a higher accuracy, and others. Therefore, a reduction in size of a photoelectric conversion element and/or a transistor constituting a pixel has been advanced. Since a quantity of signal charges that can be stored in the photoelectric conversion element is decreased when a reduction in size advances, each pixel tends to become sensitive to various kinds of noises, such as thermal noise, dark current noise, and crosstalk of light.
Jpn. Pat. Appln. KOKAI Publication No. 2005-129965 discloses a solid-state imaging device that suppresses occurrence of thermal noise or dark current noise to improve a signal-to-noise (S/N) ratio of an image. However, this publication does not describe about crosstalk.
A reduction in size of a photoelectric conversion element makes it difficult to allowing incident light to be condensed by a microlens to enter the photoelectric conversion element alone. According to the solid-state imaging device disclosed in the above patent document, a gate electrode of a transfer transistor is disposed to be adjacent to a photoelectric conversion element. In a solid-state imaging device having such a configuration, for example, incident light is condensed by the microlens to enter the photoelectric conversion element through a space between metal wiring lines. However, a phenomenon that the incident light irradiates not only the photoelectric conversion element but also a gate electrode of a transfer transistor disposed adjacent thereto occurs. When this phenomenon occurs, a part of the incident light causes a diffraction phenomenon at an edge of the gate electrode. Diffracted light diffracted by the gate electrode is propagated through a semiconductor substrate to reach a neighboring floating junction and/or a photoelectric conversion element. Such diffracted light produces crosstalk of light, thereby deteriorating pixel characteristics.